1. Field of the Invention
The present invention relates to a method of treating waste water or sewage and equipment for realizing the method and more specifically to a waste water treatment method by which organic substances included in waste water can be decompoased in dependence upon microorganism, that is, biological treatment.
2. Description of the Prior Art
As the methods of treating high-concentration organic waste water represented by sewage discharged from home or excrementitious matter (feces and urine) discharged from a barn, conventionally there have been adopted a method of combining of a septic tank based upon mainly anaerobic treatment and an aerobic treatment tank disposed after the septic tank for realizing trickling filter method, activated sludge method or contact aeration method, etc.
In these methods, however, there exist the following problems. (1) Since a many-hour aeration is required, the power consumption is relatively great. (2) Dilution is required. (3) Maintenance and management are troublesome. (4) The treatment and disposal of the produced sludge are difficult.
In addition, although a great amount of nitrogen, in particular, is included in the excrementitious matter, it is impossible to sufficiently eliminate the nitrogen on the basis of the conventional methods. Further, since colored substance formed by bile coloring matter mainly consisting of stercobilin is included in the excrementitious matter, and therefore it is impossible to eliminate this colored substance in dependence upon the conventional methods, this colored substance is included in the treated waste water. When this substance is discarded into rivers, the rivers are colored, thus resulting in water pollution from the standpoint of the sense of sight.
On the other hand, recently, batch-type activated sludge methods have been highlighted mainly in the small-scaled sewage treatment or operation equipment. In this method, waste water is introduced into a liquid mixed with activated sludge put in a treatment tank, and aeration, solid-liquid separation and supernatant outflow are effected in series in this treatment tank. This method has various advantages such that: (1) bulking (malsedimentation) will not occur; (2) this method is of energy saving type; and (3) no high-degree operation technique is required. Further, as compared with the conventional continuous treatment operation, it has been reported that the denitrification effect and the dephosphorization effect are high because aeration and sedimentation are repeated.
In the batch type activated sludge method, however, the high effect of denitrification has only empirically been reported, and there exists no guarantee that the high denitrification effect can always be obtained whenever the equipment is actually operated. Further, with respect to the structure of the equipment, since an overflow method cannot be adopted to flow out the supernatant waste water as in the usual continuous operation, an appropriate mechanism has so far been required.
In the method of treating life sewage, livestock waste, etc., as is represented by activated sludge method, for instance, at present, biological treatment methods based upon the metabolic action of a microorganism group have mainly been adopted. To realize these methods, conventionally the treating method such as activated sludge method or biological membrane method, in which a mixed microorganism group is cultured collectively, has been adopted. However, recently, the system in which nitrification reaction is effected is separated from that in which denitrification reaction is effected. That is, in these methods, plural treatment tanks are provided for enhancing each peculiar reaction separately. This is because it is possible to realize a condition under which a reaction peculiar to an microorganism can readily be enhanced as much as possible, that is, the treatment system can be realized in natural fashion. In order to realize such a treatment system as described above, it is necessary to devise the structure of the treatment tank. However, it is difficult to obtain the treatment function answering the object in dependence upon only the tank structure.
Further, organic substances in waste water can be decomposed by aerobically treating the waste water by activated sludge for denitrification or dephosphorization, and thereafter the treated waste water is discharged into rivers after disinfection by an antiseptic solution. However, in the case of excrementitious matter, colored substances formed by bile coloring matter mainly consisting of stercobilin are included in the finally treated waste water. Therefore, the treated and discharged waste water is colored, thus resulting in water pollution.